/Engine/Source/Editor/UnrealEd/Public/SnappingUtils.h
Snaps a location to the nearest vertex
true if anything was snapped
static bool SnapLocationToNearestVertex ( FVector & Location, const FVector2D & MouseLocation, [FLevelEditorViewportClient](API\Editor\UnrealEd\FLevelEditorViewportClient) * ViewportClient, FVector & OutVertexNormal, bool bDrawVertHelpers )